Spectral purity and reduced phase noise are becoming an inseparable requirement of signal generation and amplification circuits. Most modern communication systems, in particular, employ phase-locked loops (PLLs) and frequency synthesizers, along with their associated specified performance. Those specifications normally dictate the performance of individual blocks, including voltage controlled oscillators (VCOs), dividers, etc. Traditionally, the noise and spectral profile of different blocks are included in a linear, phase domain AC-type analysis, or simulation, to estimate the final spectral performance of a PLL. Such analysis, however, ignores the nonlinear effects in the signal generation path, including a limiting action by a limiter, for example.
Limiters may be utilized with an electric circuit to transform a sinusoidal wave into a square wave, for example. Because of the non-linear effect in the signal generation path within the electric circuit and the resulting phase noise profile, as outlined below, a limiting action by a limiter may substantially increase the phase noise profile of the generated signal at the output of the limiter.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.